The use of mixtures of fluids and abrasive solids for cleaning of surfaces is well known. Mixtures of high pressure fluids, including both liquids and gases, with abrasive particles, such as sand, are described, for example, in U.S. Pat. No. 794,122, Rosengarten; U.S. Pat. No. 2,071,472, Pletcher; U.S. Pat. No. 2,290,979, Luce; U.S. Pat. No. 2,234,250, Voerge; U.S. Pat. No. 2,325,517, Howard; and U.S. Pat. No. 2,376,616, Oechsle et al. In the last referenced patent, two separate streams are fed, one of a sand air mixture and the other of water, the two mixing before joining the surface to be cleaned. Similarly, sand is mixed with a fluid and directed against a surface to be cleaned in U.S. Pat. No. 783,218, Murray; U.S. Pat. No. 3,646,709, Nolan; U.S. Pat. No. 3,690,067, Goss et al; U.S. Pat. No. 3,828,478, Bemis; U.S. Pat. No. 3,276,168, Ashworth; U.S. Pat. No. 3,994,097, Lamb; and U.S. Pat. No. 4,369,607, Bruggeman et al.
The mixture of an abrasive with a fluid for cleaning of teeth has also been described in the prior art. For example, in U.S. Pat. No. 3,971,136, Madsen an insoluble abrasive is mixed with water and air and delivered against the surface of teeth to clean them. More recently, water soluble abrasives have been employed for the cleaning of teeth, and such soluble abrasives are believed to be advantageous because they avoid excess abrasion of the tooth enamel. For example, U.S. Pat. No. 4,214,871, Arnold shows the use of halite, in combination with water, but with no gaseous component, to clean teeth.
Water soluble abrasives have also been used for cleaning of teeth, in combination with water and a gas stream, for example, in U.S. Pat. Nos. 4,174,571 and 4,412,402, both listing Gallant as the inventor. In each of these patents, however, the water stream and the abrasive laden gas stream are delivered from separate nozzles and are mixed only at some point between their ejection from the nozzle and the surface of the tooth to be cleaned. As a consequence, even when the nozzle delivering the water stream and the nozzle delivering the abrasive laden gas stream are formed as part of a single hand piece, the distance that this hand piece must be held from the surface of the teeth to be cleaned is critical, or the two streams do not mix adequately.